The present invention relates generally to remote sensing systems. More particularly, the present invention relates to an apparatus for transmitting, reflecting, and detecting light in an open path sensing system such as a vehicle emission sensing system, having us in detecting and/or measuring one or more components of the air through which the light passes.
Current methods of determining whether a vehicle is compliant with emission standards include open path and closed path emissions measurement systems. In a closed path system, an emission sensor is directly connected to the exhaust of the vehicle, such as by insertion into a tailpipe. An open path vehicular emissions measurement system collects data by a means other than a direct connection to the tailpipe, such as a remote sensor that analyzes the individual components of emissions. Open path vehicle emission systems are often preferable to closed path systems because they can be used in numerous locations and do not require the vehicle to stop for testing.
Various open path emission sensing systems have been known. One such device uses a radiation source on one side of a roadway that projects a beam across the roadway to be received by a detector. The radiation source and the detector are located on opposite sides of the roadway. The radiation source emits light spectra that may be used to detect an emission signature by way of absorption of light, or which alternatively may be used to excite emission components so as to cause the components to emit light. The detected emission signature can then be used in various applications, such as the measurement of a vehicle""s compliance with emission limits and the determination of the type of fuel that a vehicle is using.
A disadvantage of many known arrangements is that the radiation sources and detectors must be placed on opposite sides of the roadway from each other. Since both the detectors and radiation sources require power to operate, this means that a separate power supply must be provided on each side of the roadway.
Some known arrangements have tried to overcome this problem by using a radiation source on one side of a roadway and a reflective apparatus located on the other side of the roadway.
Accordingly, it is desirable to provide an improved optical transmission, reflection, and detection system as herein disclosed.
It is therefore a feature and advantage of the present invention to provide an improved optical transmission, reflection, and detection system. In accordance with one embodiment of the present invention, a gas component analysis system includes a first light source capable of emitting at least one beam of light having known emission intensities corresponding to a plurality of infrared, visible, and ultraviolet spectra. The system also includes a reflection unit, a detection unit capable of receiving the beam and measuring received intensities corresponding to the plurality of light spectra, and a processor capable of comparing the emission intensities and the received intensities and identifying a concentration of a component corresponding to the intensities.
Preferably, the system also includes a first off-axis reflector positioned to receive the beam from the first light source and reflect the beam toward the reflection unit. The reflection unit is positioned to receive the beam from the off-axis reflector and reflect the beam. Also preferably, a second off-axis reflector is positioned to direct the beam reflected by the reflection unit so that the beam may be received by the detection unit. Each off-axis reflector preferably comprises a parabolic mirror.
Also preferably, the system also includes a filter wheel positioned to spin about an axis and receive the beam from the first light source and pass the beam to the reflection unit in pulses. The filter wheel preferably includes a plurality of filters, each of which substantially limits the passage of light to a predetermined spectral wavelength or range of wavelengths.
Also preferably, the beam of infrared light travels along an optical path to the reflection unit. In this embodiment, the system also includes a second light source capable of emitting a beam of ultraviolet light, as well as a neutral density filter positioned to direct the beam of ultraviolet light along the optical path to the reflection unit. The neutral density filter should be positioned to direct the beam of infrared light to the reflection unit.
Also preferably, the system also includes a reflector wheel positioned to spin about an axis and receive the beam from the reflection unit and direct infrared components of the beam to the detection unit in pulses.
In accordance with another embodiment, a method of measuring concentrations of one or more components of a gas includes the steps of: (1) emitting at least one beam of light having known emission intensities corresponding to a plurality of infrared, visible, and ultraviolet spectra through the gas; (2) using a reflection unit to reflect the beam; (3) using a detection unit to receive the beam; (4) measuring received intensities in the beam corresponding to the plurality of light spectra; and (5) identifying a concentration of at least one component of the gas corresponding to a ratio of the emission intensities and the received intensities.
Preferably, the method embodiment also includes, before the reflecting step, filtering the beam and passing the beam to the reflection unit in pulses. It may also include, before the detecting step, directing visible and ultraviolet components of the beam and directing infrared components of the beam to the detection unit Also preferably, in the method embodiment the identifying step is performed by a processing device that is programmed to perform the calculation of a component concentration using a formula corresponding to the Beer-Lambert law.
There have thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.